I can't fully answer that question until I put on a 15mm rear sway and rear subframe bushing inserts which I plan to do this weekend. As it stands right now, the car is running a 28mm E93 M3 front sway with PSS10s but no rear sway because this 128 was the non-sport suspension model. With no rear sway, I think the car is a bit unbalanced and after much deliberation, I think the 15mm rear is the right choice.

In the 3 or so autox events I have done with this 128, I can tell a diff would help but to what extent, I couldnt say. After the rear work, I'm looking at front camber and the M3 control arm kit and I think I will call it a day on handling at that point. At that point, I'll make an assessment but I seriously doubt a diff will make the cost/benefit cut. With 245/17 Star Specs or RS3s, I dont think putting the power down is a huge problem.

I can't fully answer that question until I put on a 15mm rear sway and rear subframe bushing inserts which I plan to do this weekend. As it stands right now, the car is running a 28mm E93 M3 front sway with PSS10s but no rear sway because this 128 was the non-sport suspension model. With no rear sway, I think the car is a bit unbalanced and after much deliberation, I think the 15mm rear is the right choice.

In the 3 or so autox events I have done with this 128, I can tell a diff would help but to what extent, I couldnt say. After the rear work, I'm looking at front camber and the M3 control arm kit and I think I will call it a day on handling at that point. At that point, I'll make an assessment but I seriously doubt a diff will make the cost/benefit cut. With 245/17 Star Specs or RS3s, I dont think putting the power down is a huge problem.

Congrats on the install. I did the same on my 128i (but with PSS9's) about a year ago. I also did camber plates at the time and, like you, I'm considering the M3 control arms. Would also like to do the M3 rear subframe bushings, which has me thinking about a rear sway bar as well (since it saves a lot of labor to do both at once).

Curious how you came up with 15 mm for the rear sway? I think the Dinan bar is 15 mm, but I don't know of any others. The stock sport suspension one (which I have) is 12 mm, and the M3 rear bar is 20 mm. I've considered Dinan's 15 mm bar since it theoretically represents a happy medium, but I don't really know if I shouldn't just stick with what I have. I'd like to hear your logic - in almost 2 years of posting to these forums, I have yet to see much of a consensus on this issue.

yeah had the bushings put in last year. the car feels much more planted in the back turning . no more wobble accelerating or braking hard either. it was definitely worth it. oem bushings are just crappy jello stuff

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"I would quote everything pixelblue said, but you've already read it. Take it from someone who's put the 1 through its paces"

Congrats on the install. I did the same on my 128i (but with PSS9's) about a year ago. I also did camber plates at the time and, like you, I'm considering the M3 control arms. Would also like to do the M3 rear subframe bushings, which has me thinking about a rear sway bar as well (since it saves a lot of labor to do both at once).

Curious how you came up with 15 mm for the rear sway? I think the Dinan bar is 15 mm, but I don't know of any others. The stock sport suspension one (which I have) is 12 mm, and the M3 rear bar is 20 mm. I've considered Dinan's 15 mm bar since it theoretically represents a happy medium, but I don't really know if I shouldn't just stick with what I have. I'd like to hear your logic - in almost 2 years of posting to these forums, I have yet to see much of a consensus on this issue.

Thanks.

Hotchkis also has a 15mm bar, but I think Tom is considering the E93 regular 3 series rear bar which is 15mm. The E9x 3 series have a 13mm, 14mm, and a 15mm rear bar depending on the model.

I got the bar from Dan at United BMW in Roswell Georgia although that was a very bad experience and although I know he has done good things for other bimmerpost folks in the past, I highly discourage anyone from going through him. If anyone wants to know the details just PM me.

I will give you guys my opinion after I get the bar installed, but with the PSS10s and a 28mm stiff front sway, I think I need a bar in the back to balance it out. The 1M gets a huge 22mm rear sway but that has an LSD - all of the other 1ers get a 12mm rear but that is a component of the relatively soft suspension setup, even on the 'sports' suspension option'd cars.